PAGE中英文對照外文翻譯文獻(文檔含英文原文和中文翻譯)PneumaticsystemandvariousvalvebasicintroductionPneumaticsystemsusepressurizedgasestotransmitandcontrolpower.Asthenameimplies,pneumaticsystemtypicallyuseair(ratherthansomeothergas)asthefluidmediumbecauseairisasafe,low-cost,andreadilyavailablefluid.Itisparticularlysafeinenvironmentswhereanelectricalsparkcouldigniteleaksfromsystemcomponents.Inpneumaticsystems,compressorsareusedtocompressandsupplythenecessaryquantitiesofair.Compressorsaretypicallyofthepiston,vaneorscrewtype.Basicallyacompressorincreasesthepressureofagasbyreducingitsvolumeasdescribedbytheperfectgaslaws.Pneumaticsystemsnormallyusealargecentralizedaircompressorwhichisconsideredtobeaninfiniteairsourcesimilartoanelectricalsystemwhereyoumerelyplugintoanelectricaloutletforelectricity.Inthisway,pressurizedaircanbepipedfromonesourcetovariouslocationsthroughoutanentireindustrialplant.Thecompressedairispipedtoeachcircuitthroughanairfiltertoremovecontaminantswhichmightharmthecloselyfittingpartsofpneumaticcomponentsuchasvalvesandcylinders.Theairthenflowsthroughapressureregulatorwhichreducesthepressuretothedesiredlevelfortheparticularcircuitapplication.Becauseairisnotagoodlubricant(containsabout20%oxygen),pneumaticssystemsrequiredalubricatortoinjectaveryfinemistofoiltheairdischargingfromthepressureregulator.Thispreventswearofthecloselyfittingmovingpartsofpneumaticcomponents.Freeairfromtheatmospherecontainsvaryingamountsofmoisture.Thismoisturecanbeharmfulinthanitcanwashawaylubricantsandthuscauseexcessivewearandcorrosion.Hence,incomeapplications,airdriersareneededtoremovethisundesirablemoisture.Sincepneumaticsystemsexhaustdirectlyintotheatmosphere,theyarecapableofgeneratingexcessivenoise.Therefore,mufflersaremountedonexhaustportsofairvalvesandactuatorstoreducenoiseandpreventoperatingpersonnelfrompossibleinjuryresultingnotonlyfromexposuretonoisebutalsofromhigh-speedairborneparticles.Thereareseveralreasonsforconsideringtheuseofpneumaticsystemsinsteadofhydraulicsystems.Liquidsexhibitgreaterinertiathandogases.Therefore,inhydraulicsystemstheweightofoilisapotentialproblemwhenacceleratinganddeceleratinganddeceleratingactuatorsandwhensuddenlyopeningandclosingvalves.DuetoNewton’slawofmotion(forceequalsmassmultipliedbyacceleration),theforcerequiredtoaccelerateoilismanytimesgreaterthanthatrequiredtoaccelerateanequalvolumeofair.Liquidsalsoexhibitgreaterviscositythandogases.Thisresultsinlargerfrictionalpressureandpowerlosses.Also,sincehydraulicsystemsuseafluidforeigntotheatmosphere,theyrequirespecialreservoirsandno-leaksystemsuseairwhichisexhausteddirectlybackintothesurroundingenvironment.Generallyspeaking,pneumaticsystemsarelessexpensivethanlessexpensivethanhydraulicsystems.However,becauseofthecompressibilityofair,itisimpossibletoobtainprecisecontrolledactuatorvelocitieswithpneumaticsystems.Also,precisepositioningcontrolisnotobtainable.Whilepneumaticpressuresarequitelowduetopressurescanbeashighas10,000psi.Thus,hydraulicscanbehigh-powersystems,whereaspneumaticsareconfinedtolow-powerapplications.Industrialapplicationsofpneumaticsystemsaregrowingatarapidpace.Underneathintroductioniswidelyusedinallkindsofpneumaticsystemvalve.Valveisawidelyusedmechanicalproductineachcountry'seconomy.Youcanfindvalvescommonlyusedinthefollowingfieldslikeoil,naturegas,coal,metallurgy,mining,refinery,pipetransportation,petrochemical,chemical,pharmacy,foodproduction,powerplant,watersupply/drainage,heatsupply,airsupply,marine,vehicle,airplane,spacecraft,military,newtech,irrigationandmanyotherflowingsystems.Thereareself-drivenvalvesandoperatedvalves.Self-drivenvalves(likesafetyvalve,reliefvalve,steamtrap,checkvalve)arefunctioningbyutilizingitsmechanicaldesignorthepressure,directionofitsflowmedium.Operatedvalves(likegatevalve,globevalve,ballvalve,butterflyvalve)arefunctioningbyactuator(manual,electric,hydraulic,pneumaticetc.)orthepressure,flowdirectionofitsmedium.Duetothedifferencesofpressure,temperature,flow,andphysical-chemicalcharacterofitsmedium,therearedifferentrequirementsindesigningandapplyingthepipelinesystem.Thereforetherearenumeroustypesofvalve.GASVALVEFromtheairvalveoperatingprinciplesofview,airvalveperformancewilldirectlyaffecttheworkofcompressortanks,airvalveforthefollowingrequirements:resistancelossessmall.Airvalvesizeandairflowresistancelossesofvalvesalwaysspeedandthesizeofthespring-loadededge.Gashigherspeed,thegreatertheenergylosses;Spring-loadededgetoolarge,thelossisgreatresistance,thesizeoftheairvalvemovementdesignguidelinestodeterminethereasonablenessofthelaw.Airvalveclosedtimely,rapid,notleakclosedtoimprovetheefficiencyofmachinesandextendeduseperiod.Longlife,workreliable.Lifeisthemainfactorrestrictingairvalveandspring-loadedvalvesquality,thegenerallong-termcontinuousoperationofthecompressorstolife80hours;Formobile,short-termorintermittentoperationofcompressors,mayrequireslightlymore.Airvalveandpiston-typecompressorsaretotheimportantcomponentsisoneofthecomponentseasilydamaged.Itwillhaveadirectimpactonthedisplacementcompressors,powerconsumptionandreliabilityofoperation,thecurrentcompressorisfastdirection,androtationalspeedlimitisoneofthekeyissuesinimprovingairvalve.Piston-typecompressorstypicallyusethe"automaticvalve"thattheairvalveisopenedandclosedvalvesonthepressureonbothsidestoachievepoor,andthereisnootherdrive.PNEUMATICVALVEPneumaticvalvesregulatethetemperatureinthecontextnominalpressureandmayadjustvariousfluids,gasesandsteam,pneumatic-valveclosed,leakagesmall.Pneumatic-valveattheroleoftheimplementingagenciescouldreachagasopenorgasshutpurposes.Pneumaticvalvesregulatethepneumaticenforcementagenciesandregulatoryvalvestwo.Enforcementagenciestopromotetheimplementationofdevicesinstalled,itcompressedair-driven,exportthrust;Regulationvalvesarepartoftheimplementationofdevicestoregulatedirectcontactwiththemedia,regulatorymediumflow.Thepneumatic-valvestructurewithsimple,reliableoperation,exportthrustlargemaintenanceconvenientandinexpensive,suchasfireblastmeritspneumatic-valvewidelyusedforchemical,oil,metallurgical,electrical,textileandotherindustrialproductionprocessesautopilotandremotecontrol.PRESSUREREGULATINGVALVEpressureregulatingvalveisarelianceonexternalenergytransfermediumitselfwaspressurechangespressure-typeautomaticadjustmentofproduct,youcanadjustthevalveinthepressureequipmentdebuggingprocessinaccordancewiththeirownprocessespressureregulatingvalvesfortheguidecommandsystemsetpressureafterpressureregulatingvalvesvalue,pressureregulatingvalveswillbenaturalgaspressureregulatingvalves,thepressureforyoutosetandautomaticallymaintainitsconstant,pressureregulatingvalvesinthecontrolroomforyourremotecontroloxygenflowdownstream.Flowwillbeusedforon-siteoxygenpressureregulationandfeedbacktocontroltheactualprocessparameterstocontrolthedistance.Youcaneasilyadjusttheoxygenpressure.氣壓系統及各種閥門的基本介紹氣壓系統是用壓力氣體傳遞和控制動力，正如名稱所表明的那樣，氣壓系統通常用空氣（不用其他氣體）作為流體介質，因為空氣是安全、成本低而又隨處可得的流體，在系統部件中產生電弧有可能點燃泄漏物的場合下（使用空氣作為介質）尤其安全。在氣壓系統中，壓縮機用來壓縮并供應所需的空氣。壓縮機一般有活塞式、葉片式和螺旋式等類型。壓縮機基本上是根據理想氣體法則，通過減小氣體體積來增加氣體壓力的。氣壓系統通常考慮采用大的中央空氣壓縮機作為一個無限量的氣源，這類似于電力系統中只要將插頭插入插座便可獲得電能。用這種方法，壓力氣體可以從氣源輸送到整個工廠的各個角落，壓力氣體可通過空氣濾清器除去污物，這些污物可能會損壞氣動組件的精密配合部件如閥和氣缸等，隨后輸送到各個回路中，接著空氣流經減壓閥以減小氣壓值適合某一回路使用。因為空氣不是好的潤滑劑（包括20%的氧氣），氣壓系統需要一個油霧器將細小的油霧注射到經過減壓閥的空氣中，這有助于減少氣動組件精密配合運動件的磨損。由于來自大氣中的空氣含不同數量的水分，這些水分是有害的，它可以帶走潤滑劑引起過分磨損和腐蝕，因此，在一些使用場合中，要用空氣干燥器來除去這些有害的水分。由于氣壓系統直接向大氣排氣，會產生過大噪聲，因此可在氣閥和執行組件排氣口安裝消聲器來降低噪聲，以防止操作人員因接觸噪聲及高速空氣粒子有可能引發的傷害。用氣動系統代替液壓系統有以下幾條理由：液體的慣性遠比氣體大，因此，在液壓系統中，當執行組件加速減速和閥突然開啟關閉時，油液的質量便是一個潛在的問題，根據牛頓運動定律（力等于質量乘以加速度），產生加速運動油液所需力要比加速同等體積空氣所需的力高出許多倍。液體比氣體具有更大的粘性，這會因為內摩擦而引起更大的壓力和功率損失；另外，由于液壓系統使用的液體要與大氣隔絕，故它們需要特殊的油箱和無泄漏系統設計。氣壓系統使用可以直接排到周圍環境中的空氣，一般來說氣壓系統沒有液體系統昂貴。然而，由于空氣的可壓縮性，使得氣壓系統執行組件不可能得到精確的速度控制和位置控制。氣壓系統由于壓縮機局限，其系統壓力相當低（低于250psi），而液壓力可達10000psi之高，因此液壓系統可以是大功率系統，而氣動系統僅用于小功率系統。下面介紹廣泛應用于氣壓系統的各種閥門。閥門是國民經濟建設中使用極為廣泛的一種機械產品。閥門在石油、天然氣、煤炭、冶金、和礦石的開采、提煉加工和管道輸送系統中；在石油化工、化工產品，醫藥和食品生產系統中；在水電、火電和核電的電力生產系統中；在城建的給排水、供熱和供氣系統中；在冶金生產系統中；在船舶、車輛、飛機、航天以及各種運動機械的使用流體系統中；在國防生產以及新技術領域里；在農業排灌系統中都有大量的需求。閥門分